JP 2013-240176A discloses a power supply device that includes a DCDC converter including an output inductor, and a power supply control portion that feeds back the output voltage of the DCDC converter and sets the duty ratio of a pulse-modulated pulse signal, and controls the output voltage based on the pulse width modulation. The power supply control portion is configured to, when changing the output voltage, gradually change the voltage command value provided to the DCDC converter with a value less than or equal to the maximum command value variation every output voltage receiving period.
The power supply device described above performs control so as to adjust the degree to which the voltage is increased or decreased by the DCDC converter such that the output voltage reaches the designated target voltage. As the method for controlling the degree to which the voltage is increased or decreased, a method is known in which the degree to which the voltage is increased or decreased is controlled by adjusting the duty ratio of a PWM signal provided to a switching element of the DCDC converter. The output voltage can be brought closer to the target voltage by, for example, when the output voltage is lower than the target voltage, making an adjustment so as to increase the duty ratio of the PWM signal such that the output voltage will be higher than the target voltage, or when the output voltage is higher than the target voltage, making an adjustment so as to reduce the duty ratio of the PWM signal such that the output voltage will be lower than the target voltage.
However, when the duty ratio of the PWM signal is feedback controlled so as to bring the output voltage closer to the target voltage while monitoring the output voltage as described above, the problem arises that feedback control is not performed appropriately when the detection value of the output voltage indicates an anomaly for some reason. For example, if a detection anomaly in which the detection value of the output voltage indicates 0 V occurs while lowering the voltage (buck control) from the high voltage power supply side toward the low voltage power supply side, simply performing the above-described feedback control causes the processing of increasing the duty ratio of the PWM signal to be continuously performed, and in the end, the duty ratio reaches 1 (i.e., 100%) excluding the deadtime. That is, a similar level of voltage as the input voltage is output, and a problem arises in that an excessively high voltage is output to low voltage power supply side. This problem occurs not only when buck control is performed, but also when boost control is performed.
The present disclosure has been made under the circumstances described above, and it is an object of the present disclosure to provide a voltage converting device that can detect an anomaly in which the duty ratio provided to the voltage converting portion does not converge to a normal range.